This invention relates to apparatus for printing video signal information using ink drops. More particularly, it relates to such an apparatus which does not produce stains on the writing medium during unstable operation thereof, particularly at starting.
The typical ink drop writing apparatus is constructed such that ink is emitted in the form of a stream which is subsequently separated into ink drops. The ink drops are electrostatically deflected while flying, the deflected ink drops adhere to desired positions on a writing medium, and an information is recorded by the combination of "dots" formed by the adhesion of the ink drops on the writing medium.
In order to perform the electrostatic deflection of the ink drops, an electrostatic force is generally utilized. More specifically, charges in an amount corresponding to the desired or required amount of deflection are bestowed on the ink drops, and the charged drops are subjected to an electrostatic force while flying in a predetermined electrostatic field (in a space between two electrode plates across which a voltage is applied). The ink drops unnecessary for the recording are captured by a waste catcher, and do not reach the writing medium. In the case where the ink drops are to be deflected in only one direction with respect to the direction of rectilinear advance (no deflection), the waste catcher is located at a rectilinear-advance position. In the case where it is desired to make the amount of deflection large, the ink drops are deflected bidirectionally with respect to the rectilinear advance. At this time, it is common that the waste catcher is located at a predetermined (maximum) deflection position in either direction.
In the bidirectional deflection system, the ink drops unnecessary for the recording need to be deflected to the position of the waste catcher with at least a minimum degree of reliability. Disadvantageously, however, the separation and creation of the ink drops is unstable and an accurate deflection cannot be obtained during the starting-up operation of the ink drop writing apparatus, so that the ink drops miss the waste catcher and stain the apparatus as well as the writing medium.